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Discussion Starter #1
I’m confused. Can anyone definitively answer:

1. Can you pre-condition the battery of an i3 using a 10amp 3-pin charger? I appreciate that cabin conditioning uses car battery to heat/cool the cars interior but what about pre-conditioning the cars 94Ah battery?


2. I understand (from Ohme) that the Ohme charger is not compatible or programmed to deal with battery pre-conditioning. As far as I understand it, once the Ohme charger charges the battery to 100% it shuts itself off and is unable to provide any more power. Are any home 7kw smart chargers able to deal with Pre-conditioning? If so, which ones?

Thanks in advance.
 

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In answer to question #1, yes.

The i3 has the potential to draw so much power during preconditioning that it always draws from the battery. The requirement is that he car be connected to an EVSE (or more specifically a LIVE EVSE), with the expectation that rate of charge may not be able to keep up with demand.
 

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2020 BMW i3S 120Ah BEV
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How does the Ohme have any idea what the car battery state is? If it's anything like my juicenet charger app that's just a pain as it tries to guess the charge state of the battery and then forcibly disconnects the car when it thinks it's full. It has no way of knowing, so I'd suggest you let the car take what it needs. Any excess it'll pull from the HV battery as it needs, nothing much you can do about that.
 

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Discussion Starter #4
How does the Ohme have any idea what the car battery state is? If it's anything like my juicenet charger app that's just a pain as it tries to guess the charge state of the battery and then forcibly disconnects the car when it thinks it's full. It has no way of knowing, so I'd suggest you let the car take what it needs. Any excess it'll pull from the HV battery as it needs, nothing much you can do about that.
The Ohme app gets access to the connected drive account as you provide the Ohme app with your BMW login when setting up. Therefore it has all the range and battery state of charge info. What I have found is even if you set a finish time on the Ohme app (for example 10am) and select the same departure time in the car (for pre-con purposes) even though the Ohme suggests it is working towards a full charge at 1000 it almost always finishes at least 2 hours earlier again making pre-con impossible. The i3 DOES NOT use its battery to pre-condition the battery (don’t forget there’s a difference between cabin conditioning and battery conditioning - I’m concerned with battery conditioning or warming the battery to 10deg to maximise its departure range and life span although cabin conditioning is the final part of the process but can be selected separately and that does use the car’s battery) therefore it needs an external power source to complete the job.
 

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In answer to your points...

1. No - the pre-conditioning is drawing more power than the 3 pin charger can cope with and therefore starts using the car's battery power. Believe me, I've tried... the app will say 100% before pre-con starts, and when pre-con is over, and I'm ready to start my journey, the charge % has gone down to about 92-94%.

2. I have a pod point 7kw that more than copes with pre-con and gives me 100%, a pre-con battery and a nice warm car when I unplug and start my journey.
 

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Discussion Starter #6
In answer to your points...

1. No - the pre-conditioning is drawing more power than the 3 pin charger can cope with and therefore starts using the car's battery power. Believe me, I've tried... the app will say 100% before pre-con starts, and when pre-con is over, and I'm ready to start my journey, the charge % has gone down to about 92-94%.

2. I have a pod point 7kw that more than copes with pre-con and gives me 100%, a pre-con battery and a nice warm car when I unplug and start my journey.
1. further study since initially posting reveals that battery pre-con requires a min of 10amp/ 220v so it does on a 3-pin plug. Found that in David Bricknell’s excellent book.
2. Is your Pod-Point a smart charger? What does it do when the car is fully charged? I presume it doesn’t switch itself off and refuse to restart once a pre-con power demand is made?
 

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1. further study since initially posting reveals that battery pre-con requires a min of 10amp/ 220v so it does on a 3-pin plug. Found that in David Bricknell’s excellent book.
2. Is your Pod-Point a smart charger? What does it do when the car is fully charged? I presume it doesn’t switch itself off and refuse to restart once a pre-con power demand is made?
1. Ok - cool - but I'd never use the supplied 3 pin charger for pre-con when I've got a pod point as well.

2. Yes my pod is a smart charger. When the car is fully charged, it switches itself off. When a pre-con is started it switches itself back on.
 

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Discussion Starter #8
Excellent. Thanks for the reply. The smart charger switching on for pre-con issue is very helpful info.
 

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1. further study since initially posting reveals that battery pre-con requires a min of 10amp/ 220v so it does on a 3-pin plug. Found that in David Bricknell’s excellent book.
2. Is your Pod-Point a smart charger? What does it do when the car is fully charged? I presume it doesn’t switch itself off and refuse to restart once a pre-con power demand is made?
Off topic, but thinking of getting David Bricknell’s book. It’s a few years old now (2016?j so is it still relevant to the 120Ahr i3?
 

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Discussion Starter #10
I bought the v4 2018 Kindle edition. It’s 120ah relevant but concentrates a little more on the 60/94Ah with regard to some of the graphs. To be honest, the questions I bought it for are not answered in the book (I’ve been banned from the excellent but totalitarian Facebook group - don’t get me started on that) so in hindsight it’s pretty interesting but not a lot of new info in it that I hadn’t already seen on the FB group.
 

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The Ohme app gets access to the connected drive account as you provide the Ohme app with your BMW login when setting up.
Interesting, didn't know that. Juicenet is not so smart, it just cuts power to the car when it feels like it. It's significantly stupid.

AFAIK if you set the car departure time more than 3 hours ahead of departure it will in fact pre-condition the batteries using whatever power supply it has at hand. This will take more than a 13a socket can provide, and will max out what a 7kw supply can offer too, but afaik it will do it, and use the HV battery capacity too if it needs to.
 

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The i3 DOES NOT use its battery to pre-condition the battery (don’t forget there’s a difference between cabin conditioning and battery conditioning - I’m concerned with battery conditioning or warming the battery to 10deg to maximise its departure range and life span although cabin conditioning is the final part of the process but can be selected separately and that does use the car’s battery) therefore it needs an external power source to complete the job.
If you have a source to share, I'd appreciate it! Here are my sources re: the battery powering preconditioning (battery & cabin):


Tom Moloughney , Inside EVs:
(Although he doesn't name his source in this article, Tom is a well-regarded member of the larger EV community and an I3 owner. This article was published 5 years ago and is heavily referenced on various forums, so I would expect if it was factually incorrect we would have seen a correction by now.)

Q. Can you precondition the battery while the vehicle is plugged into a 120v source or does it need to be connected to a 240v source? A. 120V (Level 1/OUC) or 240V (Level 2) have the same effect in terms of preconditioning. However, if charging on Level 1, the preconditioning consumption is higher than the charge rate, therefore potentially the vehicle will not be fully charged at the departure time.

unattributed, BMW i3 Owners blog:
(The source is not disclosed, but again this is a heavily referenced article that was posted over 4 years ago and I have not seen refutes to it. Per the BMW technical training manual, the battery's electrical heating draw is 1000W, )

It can also be noted that both preconditioning (cabin and battery) are using power from the HV battery, but if the car is plugged in it will start charging the battery. However, if the car is plugged in with only a standard charger the preconditioning will use more power (approx. 4000W) than what the car is able to draw from the socket and the car will hence not be fully charge at the time of departure.


From my own experience, I charge at 120v every night at work (I leave work at 11 PM) with preconditioning scheduled. During San Francisco winter our "cold" nights get down to 40° F / 4° C on the edge of the bay. I've returned to my car, which earlier reached 100%, but at departure time decreased to 95%, and according to the battery temperature in the i3's "hidden menu" it has been warmed to 68° F / 20° C.
 

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Discussion Starter #13
Source: David Bricknell’s book on the i3. Bit of a bible to the i3 UK Facebook group and he credits Tom Moloughney in the opening credits of that book.
The car must be plugged into a main elec supply (in the UK 230v) to pre-con.
 

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So I believe we are in agreement.

1. The car must be plugged in.

2. The battery serves as the power reservoir, and the charging system back-fills as needed.

I would also add that residual heat generated by the charging process (higher output L2 EVSEs, presumably), effectively assist in performing the battery, if the charging session is timed such that it is active leading up to the scheduled departure time.

Now, from the i3 electrical diagrams alone, there's no telling what magic happens once the AC from the charge enters the EME (or the KLE, depending on model), a far as how the car mixes AC input and battery supply. But it's clear the only requirement is that the car needs to be plugged in; the AC input does not need to meet the demand of the heating load.
 

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Discussion Starter #15
That’s what I always maintained. The car must be plugged in to pre-con. In effect using the power from the charger to condition the battery. It cannot so this if the car is not plugged in therefore requires external power to do it. The frustrating thing for me is the fact the Ohme charger (doubt you have them or their benefits in the US) can not cope with pre-con (even the 7Kw version) as once the battery is at 100% the charger shuts down. Ohme suggest it won’t come back on again if the battery level drops (for example at pre-con) making their wonderful charger pretty rubbish (or trash as you’d call it)!
 

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Going from Bricknell's book the battery heater which is used to precondition the battery has a 1KW heater element and requires a minimum of a 220v/10A supply and will heat the battery to around 10 degrees C. The Cabin heater is 5KW and so unless your charger can provide at leat 7KW then you may not have 100% chagre when you leave as the battery will have been used to heat the cabin. AFAIK you can't precondition (Heat) the battery from itself (i.e. when it is not plugged into a charger).
 

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To be frank I'm much more interested in the comment above that Ohme can read the battery state from the BMW connected account, and the implication that there's an API to reading that .. anyone done any experimentation to pull the data themselves? I find the app and iDrive disappointing on the amount of data it generates about journeys and battery state, considering what it could have been.

Ooo .. i just found this ..
 

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Discussion Starter #19
Also interested in how the Ohme reads the battery state. Any insight into how this is done?
As I said before, when you register the charger on the Ohme app, you tell it what car you have and also input the connected drive username and password. That gives the Ohme app access to your cars details? I assume that’s how it works?
 

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As I said before, when you register the charger on the Ohme app, you tell it what car you have and also input the connected drive username and password. That gives the Ohme app access to your cars details? I assume that’s how it works?
It should be noted that during charging the figure obtained from ConnnectedDrive is an estimate based on the starting status, the charge rate and the time charging. The car updates it every so often (20-30 minutes), but the slow increment is a best guess. I ran some experiments ramping the charge rate (5A increments every 15 minutes I think) and didn't see any change in charge rate until the car updated the server, at which point the SoC would jump up and the time to complete was recalculated.
 
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